Degradation mechanism of ferroelectric properties in Pt/Bi4-xLaxTi3O12/Pt capacitors during forming gas annealing

Degradation mechanism of ferroelectric properties in the Pt/Bi4-xLaxTi3O12/Pt (Pt/BLT/Pt) capacitors during forming gas annealing (FGA) was systematically investigated by examining ferroelectric responses and spatial distributions of relevant species using secondary ion mass spectrometry. It was shown that the degradation of ferroelectric properties during FGA was not originated from the oxygen loss induced by a reducing atmosphere but was mainly caused by protons catalytically dissociated from molecular hydrogen (H-2) by the top Pt electrode. The following sequential mechanism has been identified from the present study: (i) the adsorption and dissociation of H-2 to produce protons and electrons by the top Pt electrode, (ii) the columnar penetration of protons into the BLT film, accelerated by the region of negatively charged Bi-site vacancies near the bottom electrode, and (iii) the decomposition of perovskite phase after FGA at 400 degreesC. (C) 2001 American Institute of Physics.